Lamp driving apparatus having balance circuit units for a display

Abstract

A lamp driving apparatus wherein a plurality of two-winding balance circuits are connected to a plurality of parallel-connected lamp groups so that all of the lamps may be illuminated even though ambient conditions cause some of the lamps to have low resistance. Capacitors are connected to first electrodes and certain of the balance coil windings are connected to second electrodes of one of the lamp groups while, in a second lamp group, others of the balance coil windings are connected to the first electrodes and capacitors are connected to the second electrodes thereof, current flowing through balance coil windings to some lamps being affected by current flowing through balance coil windings to other lamps.

1. A lamp driving apparatus, comprising:
 a plurality of two-electrode lamps arranged in groups; 
 a plurality of two-winding balance coils with each corresponding to one of the plurality of two-electrode lamps; 
 a plurality of capacitors, and 
 a transformer having two secondary windings; 
 wherein first capacitors are connected to first electrodes of a first lamp group and first windings of first balance coils are connected to second electrodes of the first lamp group, and 
 first windings of second balance coils are connected to first electrodes of a second lamp group and second capacitors are connected to second electrodes of the second lamp group so that current flowing through the two-winding balance coils to some lamps is affected by current flowing through balance coils to others of the lamps, 
 wherein the first balance coils are connected to one of the secondary windings of the transformer, and the second balance coils are connected to the other of the secondary windings of the transformer. 
 
   
   
     2. A lamp driving apparatus according to  claim 1 , wherein second windings of the first balance coils are connected in a series loop, and second windings of the second balance coils are connected in series loop. 
   
   
     3. A lamp driving apparatus according to  claim 1 , wherein current flowing through balance coils for the first lamp group is affected by current flowing through balance coils for the second lamp group. 
   
   
     4. A lamp driving apparatus according to  claim 1 , further including an DC/AC inverter unit; and a transformer connected between said DC/AC inverter unit and said plurality of balance coils and capacitors. 
   
   
     5. A lamp driving apparatus, comprising:
 a plurality of two-electrode lamps arranged in groups; 
 an inverter unit for applying a driving voltage to the plurality of lamps; 
 a transformer having two secondary windings; and 
 a balance circuit unit connected between an output terminal of the transformer and input terminals of the plurality of lamps for uniformly supplying a current to the plurality of lamps, 
 wherein the plurality of lamps are connected in parallel with the inverter unit, the balance circuit unit has a plurality of capacitors and a plurality of two-winding balance coils with each two-winding balance coil corresponding to one of the plurality of two-electrode lamps, and a first voltage output from one of the secondary windings is applied to the first electrode of each of the lamps, and a second voltage from the other of the secondary windings of which the phase is opposite to that of the first voltage output is applied to the second electrode of each of the lamps; 
 wherein each of the plurality of lamps comprises: 
 a lamp tube; 
 first and second electrodes formed at both ends of the lamp tube; 
 a first lamp group including lamps with capacitors connected to the first electrodes thereof and with the corresponding two-winding balance coils connected to the second electrodes thereof; and 
 a second lamp group including lamps with the corresponding two-winding balance coils connected to the first electrodes thereof and with capacitors connected to the second electrodes thereof. 
 
   
   
     6. The apparatus as claimed in  claim 5 , wherein the inverter unit comprises:
 a DC/AC inverter for converting a DC voltage supplied from the outside into an AC voltage; 
 the transformer for converting the level of the AC voltage output from the DC/AC inverter; and 
 a controller for controlling the operation of the DC/AC inverter. 
 
   
   
     7. The apparatus as claimed in  claim 5 , wherein the capacitor includes a ballast capacitor. 
   
   
     8. The apparatus as claimed in  claim 5 , wherein the transformer comprises:
 a first winding connected to the DC/AC inverter; 
 a second winding for inducing the first voltage; and 
 a third winding for inducing the second voltage. 
 
   
   
     9. The apparatus as claimed in  claim 5 , wherein the lamps of the first lamp group and those of the second lamp group are alternately arranged. 
   
   
     10. The apparatus as claimed in  claim 9 , wherein at least two lamps of the same lamp group are arranged to be adjacent to each other. 
   
   
     11. The apparatus as claimed in  claim 5 , wherein a voltage output from the transformer is applied to any one of the first and second electrodes of each of the lamps. 
   
   
     12. The apparatus as claimed in  claim 11 , wherein a capacitor or balance coil is connected to the other electrode of each of the lamps. 
   
   
     13. The apparatus as claimed in  claim 12 , wherein the plurality of lamps comprise:
 a first lamp group including lamps with capacitors connected to the other electrodes thereof; and 
 a second lamp group including lamps with the corresponding two-winding balance coils connected to the other electrodes thereof. 
 
   
   
     14. The apparatus as claimed in  claim 13 , wherein the lamps of the first lamp group and those of the second lamp group are alternately arranged. 
   
   
     15. The apparatus as claimed in  claim 14 , wherein at least two lamps of the same lamp group are arranged to be adjacent to each other. 
   
   
     16. A liquid crystal display (LCD), comprising:
 a backlight unit having a lamp driving apparatus including: 
 a plurality of two-electrode lamps, 
 an inverter unit for applying a driving voltage to the plurality of lamps, 
 a transformer having two secondary windings; and 
 a balance circuit unit connected between an output terminal of the transformer and input terminals of the plurality of lamps for uniformly supplying a current to the plurality of lamps, the plurality of lamps being connected in parallel with the inverter unit, the balance circuit unit having a plurality of capacitors and a plurality of two-winding balance coils with each two-winding balance coil corresponding to one of the plurality of two-electrode lamps; and 
 an LCD panel positioned on the backlight unit to display an image thereon, wherein a first voltage output from one of the secondary windings is applied to the first electrode of each of the lamps, and a second voltage from the other of the secondary windings of which the phase is opposite to that of the first voltage output is applied to the second electrode of each of the lamps, 
 wherein each of the plurality of lamps comprises: 
 a lamp tube; 
 first and second electrodes formed at both ends of the lamp tube; 
 a first lamp group including lamps with capacitors connected to the first electrodes thereof and with the corresponding two-winding balance coils connected to the second electrodes thereof; and 
 a second lamp group including lamps with the corresponding two-winding balance coils connected to the first electrodes thereof and with capacitors connected to the second electrodes thereof.